Cannot Save Blueprint if Get All Actors of Class In Param is a Level Class

When trying to get all actors of a level class, the blueprint that the node is contained in cannot be saved.

1. Open the editor (First Person Project)
2. Open the first person character blueprint
3. Add a Get All Actors of Class node
4. Set the Actor Class to FirstPersonExampleMap_C
5. Attempt to save

Result: Error appears on saving: